variable defined in loop

Benchmark created by James on

Description

Checking performance of variable defined in for vs inside.

Preparation HTML

<script>
  // Populate the base array
  var arr = [];
  for (var i = 0; i < 1000; i++) {
    var user = {
      firstName: "bob",
      lastName: "jones"
    }
    arr.push(user);
  }
</script>

Test runner

Ready to run.

Testing in
TestOps/sec
Variable defined inside of loop
for (var i = 0; i < arr.length; i++) {
  var o = arr[i++];
  var fullName = o.firstName + o.lastName;
}
ready
Variable defined In the loop
for (var o, i = 0; o = arr[i++];) {
  var fullName = o.firstName + o.lastName;
}
ready
Variable set inside the loop
var o;
for (var i = 0; i < arr.length; i++) {
  o = arr[i++];
  var fullName = o.firstName + o.lastName;
}
ready
No variable
for (var i = 0; i < arr.length; i++) {
  var fullName = arr[i].firstName + arr[i].lastName;
}
ready
Log variable defined inside loop
for (var i = 0; i < arr.length; i++) {
  var o = arr[i++];
  console.log(o);
}
ready
Log variable defined in the loop
for (var o, i = 0; o = arr[i++];) {
  console.log(o);
}
ready

Revisions

You can edit these tests or add more tests to this page by appending /edit to the URL.